terom@132: # libpngtile
terom@28: 
terom@28: Constant-time/memory tile-based handling of large PNG images.
terom@28: 
terom@132: ## About
terom@132:     pngtile is a C library (and associated command-line utility) offering efficient random access to partial regions of
terom@28:     very large PNG images (gigapixel range).
terom@28: 
terom@28:     For this purpose, the library linearly decodes the PNG image to an uncompressed memory-mapped file, which can then
terom@28:     be later used to encode a portion of this raw pixel data back into a PNG image.
terom@28: 
terom@132: ## Notes
terom@28:     The command-line utility is mainly intended for maintining the image caches and testing, primary usage is expected
terom@28:     to be performed using the library interface directly. A simple Cython wrapper for a Python extension module is
terom@28:     provided under python/.
terom@28: 
terom@28:     There is a separate project that provides a web-based tile viewer using Javascript (implemented in Python as a
terom@28:     WSGI application).
terom@28: 
terom@73:     The .cache files are not portable across different architectures, nor are they compatible across different cache
terom@73:     format versions.
terom@73: 
terom@73:     The library supports sparse cache files. A pixel-format byte pattern can be provided with --background using
terom@73:     hexadecimal notation (--background 0xFFFFFF - for 24bpp RGB white), and consecutive regions of that color will
terom@73:     be omitted in the cache file, which may provide significant gains in space efficiency.
terom@29: 
terom@132: ## Build
terom@28:     The library depends on libpng and pthreads. The code was developed and tested using:
terom@132:         
terom@132:         * libpng12-dev      png.h       1.2.15~beta5-3ubuntu0.1
terom@132:         * libc6-dev         pthread.h   NPTL 2.7 (glibc 2.7-10ubuntu5)
terom@28: 
terom@156:     To compile:
terom@28: 
terom@132:         $ make
terom@132: 
terom@123:     The libpngtile.so and pypngtile.so libraries will be placed under lib/, and the 'pngtile' binary under bin/.
terom@123: 
terom@132: ## Usage
terom@28:     Store the .png data files in a directory. You must have write access to the directory when updating the caches,
terom@28:     which are written as a .cache file alongside the .png file.
terom@28: 
terom@28:     Provide any number of *.png paths as arguments to the ./bin/util command. Each will be opened, and automatically
terom@28:     updated if the cache doesn't exist yet, or is stale:
terom@28: 
terom@74:         pngtile -v data/*.png
terom@73:     
terom@73:     Use -v/--verbose for more detailed output.
terom@73: 
terom@28: 
terom@74:     To render a tile from some image, provide appropriate -W/-H and -x/-y options to pngtile:
terom@28:         
terom@74:         pngtile data/*.png -W 1024 -H 1024 -x 8000 -y 4000
terom@28: 
terom@28:     The output PNG tiles will be written to temporary files, the names of which are shown in the [INFO] output.
terom@28: 
terom@28: 
terom@28:     To force-update an image's cache, use the -U/--force-update option:
terom@28: 
terom@74:         pngtile --force-update data/*.png
terom@28: 
terom@73:     Alternatively, to not update an image's cache, use the -N/--no-update option.
terom@28: 
terom@132: ## Issues
terom@28:     At this stage, the library is primarily designed to handle a specific set of PNG images, and hence does not support
terom@28:     all aspects of the PNG format, nor any other image formats.
terom@28: 
terom@28:     The pt_images opened by main() are not cleaned up before process exit, due to the asynchronous nature of the tile
terom@28:     render operation's accesses to the underlying pt_cache object.
terom@28: 
terom@132: # pypngtile
terom@132: 
terom@132: Python extension for pngtile
terom@132: 
terom@132: ## Dependencies
terom@132: 
terom@132:     * python-cython
terom@132:     * python-dev
terom@132: 
terom@157: ## Development
terom@132: 
terom@132:     $ python setup.py build_ext
terom@132: 
terom@157: ## Install
terom@163:     $ virtualenv /opt/pngtile
terom@163:     $ make -B install PREFIX=/opt/pngtile
terom@163:     $ /opt/pngtile/bin/pip install -r requirements.txt
terom@157:     $ /opt/pngtile/bin/python setup.py build_ext -I /opt/pngtile/include -L /opt/pngtile/lib -R /opt/pngtile/lib
terom@157:     $ /opt/pngtile/bin/python setup.py install
terom@132: 
terom@157: